Dermatology Made Easy is based on the most popular topics from DermNet NZ's vast array of material. The book combines the essential focus of the ‘Made Easy’ book series with the authority and knowledge base of DermNet NZ's unparalleled resources.
Author: Vanessa Ngan, Staff Writer, 2012.
What is a benzophenone?
The benzophenones are a group of aromatic ketones that have both pharmaceutical and industrial applications. They have UVB and some UVA absorbing properties and act like optical filters to block out harmful UV rays. They may be used in a sunscreen product to reduce skin damage and to retard photodegradation or extend shelf life in toiletries and plastic surface coatings.
Because they commonly cause contact allergic dermatitis, benzophenones were declared the Contact Allergen of the Year for 2014 by the American Contact Dermatitis Society (ACDS).
The four main benzophenone derivatives that have been used widely in sunscreens and cosmetics are listed below. They share similar chemical and physical properties. Often benzophenone is used in combination with other chemical absorbing sunscreens to augment and stabilise the final product.
The first contact reaction to benzophenones in sunscreen products was first documented in 1972. Benzophenone sensitivity produces classic allergic contact dermatitis as well as photocontact dermatitis. In benzophenone allergic individuals, products containing benzophenone or benzophenone derivatives may cause redness, swelling, itching and fluid-filled blisters. Symptoms may appear immediately or several days later (delayed contact and photocontact dermatitis). In severe cases anaphylaxis may occur.
In addition to allergic reactions, concerns have been raised about the relative ease of which benzophenone is absorbed into the skin and may promote generation of potentially harmful free radicals. Also, recent reports of oxybenzone having hormonal effects in animal studies has deterred some people from using sunscreen products. However these findings are not based on human studies and cannot be a reliable indicator of what happens in people. Benzophenones, including oxybenzone, combined with other sunscreen agents still provide excellent sun protection. The long-term use of these agents in sunscreens is unknown and further research is warranted.
Benzophenone allergy is diagnosed by performing patch tests with 5% benzophenone in petrolatum.
Those diagnosed with benzophenone allergy should avoid exposure to benzophenone containing products. Management of benzophenone dermatitis is as for any acute dermatitis/eczema; this may include topical corticosteroid and emollient.
Read product labels and avoid products that contain benzophenone or any of its derivatives. Ask your pharmacist for advice and a suitable alternative. Your dermatologist may have further specific advice, particularly if you are highly sensitive.
Formula: benzophenone – C13H10O
CAS number: 119-61-9
Cross reactions: none listed
Appearance: white flakes or crystals with rose like odour
Sensitiser: benzophenone and its derivatives
Patch test: 5% or 10% benzophenone in petrolatum
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